A chimpanzee injected with a mouse-human monoclonalantibody remains free of signs of HIV infection after 52 weeks,while a control animal given the same viral challenge isinfected.

The report by researchers from Repligen Corp. and Merck & Co.Inc. is a year-long follow-up on the status of the chimpinoculated with an antibody to the V3 loop of the viral coat.

The data showed that the anti-V3 antibody can preventinfection if given immediately after challenge with HIV.Another chimp inoculated with the antibody 10 minutes afterinjection with HIV "has not presented any signs of persistentvirus infection to date" after 32 weeks of observation, thescientists reported.

"These observations are direct evidence that anti-V3 loop, HIV-1-neutralizing antibody can, in the absence of other virus-specific immune responses, prevent an HIV-1 persistentinfection," the scientists concluded.

"Although the C-beta1 antibody is specific for the IIIb variantof the virus," the researchers added, "anti-V3 loop antibodiescan be elicited with broader neutralizing activity."

Data on the first chimp had been presented last June at theSeventh International Conference on AIDS. Immediately afterpresenting a follow-up report in October, Repligen(NASDAQ:RGEN) and Merck dissolved their collaboration todevelop an anti-infective MAb against AIDS. Repligenreacquired rights to the monoclonals, and Merck entered into a$13 million agreement to develop similar therapeutics withMedImmune Inc. (NASDAQ:MEDI) of Gaithersburg, Md.

Repligen, located in Cambridge, Mass., and Merck are stillcollaborating to develop a preventative AIDS vaccine based ona cocktail of V3 peptides that would induce immunity to majorHIV strains found in North America and Europe.

Repligen shares closed at $16.25, down $1.50, on Wednesday.MedImmune closed at $31.50, off 50 cents.

-- Roberta Friedman, Ph.D. Special to BioWorld

(c) 1997 American Health Consultants. All rights reserved.